Is it acceptable for my best friend to date my ex-boyfriend?

Okay, so I'm 15 and recently broke up with this boy I'd been dating for the past year. Lets call him....Geoff. We were really close and he was...well is, my first love. But Geoff changed and turned really mean, we started arguing, then one day we had a massive argument, we just stopped talking completely... show more Okay, so I'm 15 and recently broke up with this boy I'd been dating for the past year. Lets call him....Geoff. We were really close and he was...well is, my first love. But Geoff changed and turned really mean, we started arguing, then one day we had a massive argument, we just stopped talking completely and the relationship fell apart. I regret everything that happened and part of me just wants to just apologise but I know that he'd never take me back. I always cared a lot more about Geoff than he did about me.

But I went to a party a few nights ago and Geoff was there. One of my best friends was there as well, lets call her Trisha. Basically Trisha and Geoff were all over each other but at the time I wasn't too bothered because they were both completely drunk. I've been thinking about it a lot though and I know this might be really irrational but I think it would genuinely hurt me if they started dating. Trisha had already said that she thought he was "alright looking" a few months back (whilst we were still together!). I mean, Trisha is a little bit sl*tty, but I love her all the same. I don't want to kick up a fuss but at the same time she knows that I still have feelings for this boy. And part of me doesn't want her to get hurt the way I did...especially seeing as he told one of my other friends that he's only doing this to make me jealous (but I don't trust gossip).
What should I do? Is it acceptable that we've only just broken up and one of my closest friends is already considering asking him out? I know it isn't acceptable in movies, etc? :L I was considering talking to Trisha about this but maybe that would just make the situation worse? But I just don't know what to do, any advice please? Am I overreacting to this?
Update: EDIT: Um, I've always been a girl who's stood by my morals and if the situation were reversed I wouldn't dream of dating a best friends ex actually...but the situation isn't reversed so I find that irrelevant. Exactly! That's what I thought, GIRL CODE! But I wasn't sure if that was actual real life or just in... show more EDIT:
Um, I've always been a girl who's stood by my morals and if the situation were reversed I wouldn't dream of dating a best friends ex actually...but the situation isn't reversed so I find that irrelevant.
Exactly! That's what I thought, GIRL CODE! But I wasn't sure if that was actual real life or just in films? Haha :) And I really don't feel comfortable about it at all, that's my problem :/
And @Love2, Thank You :) I mean we were really serious, we were together for over a year. I geniunely loved him (and please don't tell me that I can't be in love at 15 :D )
It's just a horrible situation :(
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